Electric Monopoles do exist, like Gordianus said. Assuming the OP is talking about Magnetic monopoles, why should they exist?

To rephrase: Even though there are theories that predict the existence of magnetic monopoles, the mainstream particle theories do not. Physically there is nothing wrong with their existence, but there is no reason for them to exist, either.

To rephrase: Even though there are theories that predict the existence of magnetic monopoles, the mainstream particle theories do not. Physically there is nothing wrong with their existence, but there is no reason for them to exist, either.

Huh? Monopoles are actually a fairly generic prediction of grand unified theories, from what I understand. It's actually a large conflict between theory and observation, since obviously we don't see any. This led, in part, to the development of inflation theory, which is more or less the standard paradigm for early universe cosmology (in one incarnation or another).

I meant theories that are considered 'true' now, like QED and EWT (is that how it's called?), not GUTs. I was under the impression that currently verified theories do not predict monopoles, and the existence of monopoles in speculative TOEs and GUTs are one of their experimental testing points.

I see how that point of view did not get across in my earlier post.

Though I am confused as to how magnetic monopoles led to inflation theory?

I meant theories that are considered 'true' now, like QED and EWT (is that how it's called?), not GUTs. I was under the impression that currently verified theories do not predict monopoles, and the existence of monopoles in speculative TOEs and GUTs are one of their experimental testing points.

Though I see how that point of view did not get across in my earlier post.

Though I am confused as to how magnetic monopoles led to inflation theory?

Well while it's true that we have no direct experimental verification of GUT scale physics, and likely never will, my point is that it seems a fairly generic prediction of what must be going on at those scales. This could be false, as I obviously haven't surveyed all theories claiming to describe these energy ranges, but I think it's fairly universal.

The reason this motivated inflation theory is precisely what I stated before. If you predict a monopole density which is much larger than the observed bounds (we do have some bounds), then that's obviously a contradiction. Either the theory is wrong, or the observations are flawed (not likely, given the magnitude of the discrepency). Now, as I've mentioned monopoles seem to be a fairly straightforward prediction of what's going on at GUT energies, so there's no clear way to get around producing them. The only way to lower the density, then, is to dilute them over a larger volume; this is precisely what inflation does.

Electric Monopoles do exist, like Gordianus said. Assuming the OP is talking about Magnetic monopoles, why should they exist?

To rephrase: Even though there are theories that predict the existence of magnetic monopoles, the mainstream particle theories do not. Physically there is nothing wrong with their existence, but there is no reason for them to exist, either.

You don't actually need to 'have' magnetic fields at all. The force that we call magnetism can be accounted for by the relativistic effects on moving charges. None of it's real- it's just models and we choose the one that suits a situation best.

You don't actually need to 'have' magnetic fields at all. The force that we call magnetism can be accounted for by the relativistic effects on moving charges. None of it's real- it's just models and we choose the one that suits a situation best.

How's that relevant to whether magnetic monopoles exist or not? Whatever is the way you account it for you still can measure what is called sink and source, positive and negative, or north and south pole. The question I have for you is how many poles can you count on that image above of magnetic field due to moving charge, and can you point where is the south and where is the north pole?

My point was that an argument based on fields need not be totally valid (sufficient?) once you realise that the field concept is only a concept. I know that post of yours is a great way to show that monopoles "can't" exist, based on the model that field lines have no 'ends'. But field lines are only a construct to model what we observe. The question of the existence of the monopole may require more than a field line argument.

My point was that an argument based on fields need not be totally valid (sufficient?) once you realise that the field concept is only a concept. I know that post of yours is a great way to show that monopoles "can't" exist, based on the model that field lines have no 'ends'. But field lines are only a construct to model what we observe. The question of the existence of the monopole may require more than a field line argument.

I'm not talking about "models" or "constructs". This is real.
Take a permanent magnet in your hand and you can measure it.

Staff: Mentor

Re: monopoles

Ultimately the question is an experimental one. We can construct theories in which magnetic monopoles and monopole-type magnetic fields exist (for which ##\nabla \cdot \vec B \ne 0##). However, to date nobody has actually found such particles or fields. Maybe next http://www.nature.com/nature/journal/v429/n6987/full/429010a.html someone will actually detect them convincingly, and then we will have to rewrite Maxwell's equations etc.

The statement that field lines have no ends is identical to the statement that there are no monopoles. It's not an explanation.

Furthermore, all at Tris_d has shown is that in the situation he describes there are no monopoles, not that there are no monopoles anywhere.

Actually, magnetic field due to moving charge looks like monopole to me. I see only one pole there and it certainly does not look like a dipole. I've been saying that for quite a few years now, but people are dismissing it and I never got any reasonable response. Could it be too simple to be believed, right under everyone's nose?